A21 · Hidden Voice Recorder

A21 Keychain Voice Recorder

The A21 records conversations through a built-in microphone concealed in a leather keychain. Start recording manually, set a schedule or use sound activation to capture audio when the room becomes active. Its flash memory holds up to 300 hours of audio at 8 kHz with 2-bit ADPCM compression. The recorder measures 55 mm across and 11 mm thick and weighs 21 g.

Manual, sound-activated and scheduled recording.
Up to 120 hours of battery life at 8 kHz without compression under ideal conditions. Actual runtime varies with use.
Encrypted recordings with password protection.
Date and time stamps with digital signatures.
USB charging and dedicated PC software.

Product code: A21

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Recording Controls in a Leather Keychain

Schedule a recording

Set a one-time session or a daily start and stop time. The built-in clock and calendar add a timestamp to each recording.

Skip the silence

Sound activation saves storage during quiet periods. When transferring recordings, choose whether to restore the silent intervals or skip them for faster playback.

Protect recorded audio

Password protection restricts access to content and settings. Digital signatures identify the recorder and help detect changes to recorded files.

Full Description

A compact recorder with a built-in microphone

The A21 houses a Tiny-series digital recorder inside a round leather keychain. Audio is saved to internal flash memory for transfer to a computer, with no separate microphone needed.

Its audio frequency range is 100 Hz–10 kHz. The built-in microphone can pick up speech from approximately 7–9 meters (23–30 feet) away under favorable acoustic conditions. Voice level, background noise and the recorder’s position affect intelligibility.

Manual, scheduled and sound-activated recording

Use manual activation for an immediate recording, or program a one-time or daily session. The Voice Activating System (VAS) reduces the storage used during pauses while retaining information about their duration.

During transfer, the software can restore those intervals as silence to preserve the original timeline, or omit them for a shorter playback file. An LED indicates the recorder’s operating status.

PC software and protected files

The dedicated multilingual software handles recording settings, audio export and firmware updates. Memory can be divided between recordings and other files, allowing the A21 to serve as a flash storage device as well.

Recordings are encrypted and password-protected. Each file includes its start date and time and a digital signature for recorder identification and file integrity checks.

Storage capacity and battery life

The A21 stores up to 300 hours of audio at an 8 kHz sample rate with 2-bit ADPCM compression. This is storage capacity, not battery runtime.

The 240 mAh lithium-polymer battery provides up to 120 hours of recording at 8 kHz without compression under ideal conditions. Actual runtime varies with use. It recharges through the USB connection.

In VAS mode, battery life can reach up to 400 hours under ideal conditions while the audio remains below the activation threshold. This is time spent waiting for sound, not 400 hours of continuous recording; runtime changes as recording becomes active.

Technical Specifications

Audio and Recording
Product code	A21 — Tiny series
Microphone	Built in
Audio frequency range	100 Hz–10 kHz
Voice pickup distance	Approximately 7–9 m (23–30 ft) under favorable acoustic conditions
Recording modes	Manual, sound-activated (VAS) and scheduled
Scheduling	One-time and daily start/stop timers
VAS pause handling	Restore silent intervals or skip them during transfer to a PC
Audio storage	Up to 300 hours at 8 kHz with 2-bit ADPCM compression
Memory type	Internal flash memory
Recording protection	Encryption and password protection
File identification	Start date, time and digital signature
Status indicator	LED

Power, Software and Dimensions
Battery	240 mAh rechargeable lithium-polymer battery
Charging	USB
Recording battery life	Up to 120 hours at 8 kHz without compression under ideal conditions. Actual runtime varies with use.
VAS battery life below threshold	Up to 400 hours under ideal conditions with audio below the activation threshold. Not continuous recording time; actual runtime varies with use.
Interface	USB 1.1
Data transfer rate	Up to 5.5 Mbit/s
Software	Multilingual PC software for configuration, audio export and firmware updates
Operating systems	Windows 2000 and XP; compatibility with later versions requires confirmation
File storage	Memory can be allocated between audio recordings and other files
Case	Leather keychain case
Dimensions	55 mm diameter × 11 mm thick (approximately 2.17 × 0.43 in)
Weight	21 g (approximately 0.74 oz)
Included	Recorder, USB cable, driver/software CD, user manual and wooden presentation box

Applications

Conversations and meetings

The leather keychain format keeps the recorder compact and easy to carry. The built-in microphone captures speech, and timestamps help organize recordings from different meetings.

Recurring recording sessions

Daily timers suit activities that take place at predictable times. Once configured, the recorder starts and stops each scheduled session without manual activation.

Audio with long pauses

VAS saves storage when conversations are intermittent. Restore the silent intervals to retain the original timing, or skip them when reviewing the audio.

Frequently Asked Questions

How much audio can the A21 store?

Up to 300 hours at an 8 kHz sample rate with 2-bit ADPCM compression. Storage capacity is separate from battery life and depends on the recording settings.

How long does the battery last?

Up to 120 hours of recording at 8 kHz without compression under ideal conditions. Actual runtime varies with use. The internal 240 mAh lithium-polymer battery recharges over USB.

Does the 400-hour rating mean continuous recording?

No. It applies to VAS operation under ideal conditions while sound stays below the activation threshold. The recorder is waiting for sound during that time. Battery use changes when recording starts.

Does it start recording when someone speaks?

Yes, when VAS is enabled and the sound level exceeds the selected threshold. It detects sound level rather than speech specifically, so other noises can also trigger recording.

Can I schedule recordings?

Yes. You can set a one-time recording with a start and stop date and time, or use a daily timer for recurring sessions.

How are the recordings protected?

The A21 supports encryption and password protection. Recordings also include their start date and time and a digital signature used to identify the recorder and check file integrity.

How do I transfer recordings, and which Windows versions are supported?

Connect the recorder to a PC with the supplied USB cable and use the dedicated software to export audio and adjust settings. Windows 2000 and XP are listed in the available specifications. Compatibility with newer Windows versions has not been confirmed.